Efficiency enhancement of inverted polymer solar cells by doping NaYF4:Yb3+, Er3+ nanocomposites in PCDTBT:PCBM active layer

NaYF4:Yb3+, Er3+ nanocomposites (NCs) are synthesized by a facile solvothermal approach and doped into PCDTBT:PCBM blend as a bifunctional additive to improve peformance of inverted polymer bulk heterojunction (BHJ) solar cells. The dependence of device performance on NaYF4:Yb3+, Er3+ NCs in the blend film is investigated. The results show that the short-circuit current density is apparently enhanced by doping NaYE4:Yb3+, Er3+ NCs into the active layer while maintaining the open-circuit voltage and fill factor, leading to an increase in power conversion efficiency. NaYF4:Yb3+, Er3 NCs acts two kinds of roles for light absorption enhancement. Up-conversion (UC) emission from Yb3+ sensitized Er 3 dopants in the NaYF4:Yb3+, Er3 NCs is observed. The photocurrent generated from UC near 980 nm excitation can improve the utilization of solar photons in the near infrared (NIR). The scattering effect of NaYF4 nanoparticles (NPs) enhances the light absorption in visible region. The performance of polymer solar cell doped with NaYN:Yb-3+,Yb- Er3+ NCs is compared with that of undoped. The concept of integrating UC and scattering functionality into active layer suggests a promising and practical pathway for improving visible and NIR absorption of polymer solar cells. (c) 2014 Elsevier B.V. All rights reserved.